Fidelity

The command below calculates the fidelity between the two matrices $A$ and $B$ read from respective files of fileA and fileB saved by the ``msave'' command (or ``RDOsave'' etc.).

fidelity(fileA, fileB);

The fidelity between (N,N) density matrices $A$ and $B$ is defined by

$$\begin{split}F(A,B)=\mathrm{Tr}\sqrt{A^{\frac{1}{2}}BA^{\frac{1}{2}}}. \end{split}$$ (16)